Cross Ref > Operators

Languages Focus

Common assignment operators for languages include =, ==, and :=. An assignment operator allows you to assign a value to a variable. The value can be a literal value like "Mike" or 42 or the value stored in another variable or returned by a function.

Corel Paradox:   = ObjectPAL uses = for it's assignment operator. Syntax Example:   var  FullName String    Age SmallInt endVar FullName = "Randy Spitz" Age = 42	Java:   = Java uses = for it's assignment operator.

General Info: Round Floating Point Numbers

When comparing floating point numbers, make sure you round to an acceptable level of rounding for the type of application you are using.

Languages Focus

A comparison operator compares two values either literals as in "Hello" and 3 or variables as in X and Counter. Most languages use the same operators for comparing both numbers and strings. Perl, for example, uses separate sets of comparison operators for numbers and strings.

Corel Paradox:   =, <> Common comparison operators: = equal <> not equal < less than > greater than <= less than or equal >= greater than or equal Syntax Example: 'Does ObjectPAL evaluate the math correctly? No! If .1 + .1 + .1 = .3 Then msgInfo("", "correct") Else msgInfo("", "not correct") endIf  ObjectPAL Comparison Operators (=, <>)	Java:   ==, != The Java comparison operators are: == equal != not equal < less than > greater than <= less than or equal >= greater than or equal More Info / Comment

Languages Focus

An empty string is a zero length string, a string that is equal to null (""), or not assigned. In some languages, you can check if a string is empty by comparing it to an empty string (""). Some languages distinguish between nil and null ("") so checking if the length is 0 is easier.

Corel Paradox:   isBlank() or not isAssigned() In ObjectPAL, an empty variable can be unassigned (essentially null) or blank (equivalent to ""). You have to use both isBlank and isAssigned to check for an empty string. Syntax Example: var  s String endVar ;s = ""  ;Uncomment to test 2nd case. if isBlank(s) or not isAssigned(s) Then  msgInfo("", "empty string") endIf  ObjectPAL Empty String Check (isBlank() or not isAssigned())

Java:   IsEmpty

Languages Focus

Logical operators perform conditional and, or, and not operations. Some languages support both binary logical operators that link two and unary logical operators negate (make opposite) the truth value of its argument. Finally, some languages short circuit logic. For example, with this or that, if this is an expression returning true, then that is never executed.

Corel Paradox:  ObjectPAL logical operators: and and, as in this and that or or, as in this or that Not Not, as in Not This Like VBA, ObjectPAL never short circuits. Given the expression this or that as well as this and that, if this evaluates to false, then that is still executed. Syntax Example: ;Given expressions a, b, c, and d: if Not (a and b) and (c or d) then   ;Do something. endIf  ObjectPAL Logical Operators

Java:  Java logical operators: && and, as in this and that || or, as in this or that ! Not, as in Not This & boolean logical OR (not short circuited) | boolean logical OR (not short circuited) ?: Ternary (short for if-then-else) ~ Unary bitwise complement << Signed left shift >> Signed right shift >>> Unsigned right shift ^ Bitwise exclusiv OR Syntax Example: //Given expressions a, b, c, and d: if !((a && b) && (c || d)) {   //Do something. }

General Info: Unary Operator

An operation with only one operand (a single input). Common unary operators include + plus, - minus, and bitwise not. Some operators can function as both unary and binary operators. For example, + and - operators can serve as either.

Languages Focus

What unary operators are supported in additoin to the standard plus, minus, and bitwise not.

Corel Paradox:  The ObjectPAL unary operators are: + - Not More Info / Comment	Java:  An operation with only one operand (a single input). The Java unary operators are ++, --, +, -, ~, and !. + Indicates positive value (numbers are positive without this) - Negates an expression ++ Increment operator by 1 -- Decrement operator by 1 ! Logical complement operator (inverts the value of a boolean) ~ Bitwise inversion operator (works on integral data types) More Info / Comment